A study conducted at Johns Hopkins University of a group of 40 multiple sclerosis (MS) patients used a process called optical coherence tomography (OCT) to scan the layers of nerve fibers of the retina in the back of the eye, which become the optic nerve. The process, which uses a desktop machine similar to a slit-lamp, is simple and painless.

Results of the scans were calibrated using accepted norms for retinal fiber thickness and then compared to an magnetic resonance imaging (MRI) of each of the patient’s brains - also calibrated using accepted norms. Experimenters found a correlation coefficient of 0.46, after accounting for age differences. In a subset of patients with relapsing remitting MS, the most common form of the disease, the correlation coefficient jumped to 0.69, suggesting an even stronger association between the retinal measurement and brain atrophy.

“This is an encouraging result,” says Johns Hopkins neurologist Peter Calabresi, M.D., lead author of the study. “MRI is an imperfect tool that measures the result of many types of tissue loss rather than specifically nerve damage itself. With OCT we can see exactly how healthy these nerves are, potentially in advance of other symptoms.” In addition, says Calabresi, OCT scans take roughly one-tenth as long and cost one-tenth as much as the MRI, which means they are faster and cheaper to use in studies that track the effectiveness of new treatments for MS.

But, Calabresi cautions that optic nerve damage can point to a number of diseases and is not a unique diagnostic tool for MS. However, he says, it certainly sends up a flag suggesting that MS might be present. And since optic nerve damage is one of the first recognizable symptoms of MS, doctors have a chance to identify the disease potentially before the patient suffers the physical limitations generally associated with its advanced stages.